The purpose of processing with (usually) several processing stations is to bring a sample, taken from a patient, into a state that permits sectioning into thin layers with a microtome. Sectionability can be made possible, for example, by the fact that a medium that mechanically stabilizes the tissue is introduced (infiltrated) into the tissue in multiple successive processing steps. Alternatively, the tissue can also be frozen.
A plurality of processing stations for processing histological samples are already known from the existing art. Processing stations are known, for example, in the form of trimming stations, fixing stations, dehydration stations, cleaning stations, infiltration stations, embedding stations, or microtomes (sectioning stations), in a wide variety of embodiments.
In a trimming station, the tissue (for example, removed from a patient) is cut into individual samples. The samples are usually placed into cassettes and transported to a fixing station. Fixing of the samples is necessary because oxygen supply to the cells is interrupted after removal of the tissue from the patient, and this results in cell death. Cell death causes morphological changes that are referred to as “necrosis.” Firstly a swelling of the cells can be observed, and protein denaturing and autolysis also occur. To counteract this damage, fixing of the removed samples with a fixing agent, for example formalin, occurs in the fixing station.
After treatment in the fixing station, dehydration of the samples occurs in a dehydration station. Dehydration of the samples is necessary in order to make possible the subsequent process of infiltration and embedding.
Because the fixing agent, in particular formalin, is usually an aqueous medium, whereas the infiltration or embedding agent (in particular paraffin) that is to be used is in most cases a medium not miscible with water, dehydration of the samples must be accomplished before further processing of the samples in an infiltration station. Dehydration of the samples is performed with the aid of dehydrating agent, such as e.g. ethanol.
Prior to transfer of the samples to the infiltration station, they are also cleaned. Cleaning is necessary because water and/or alcohol contaminants in the embedding agent, in particular paraffin, result in poor cutting characteristics with a microtome and therefore need to be avoided. Saline, xylene, etc. can be used, for example, as cleaning agents.
After processing of the sample in the cleaning station, it is brought to an infiltration station. In the infiltration station an infiltration agent, which usually corresponds to the embedding agent used later, is introduced into cavities of the sample until it is saturated. Introduction of the infiltration agent allows the samples to be mechanically stabilized.
Following processing of the sample in the infiltration station, it is processed in the embedding station. In the embedding station the histological sample is embedded into an embedding agent such as paraffin or wax. In practice, the term “embedding” is used in two ways. On the one hand it is a synonym for “infiltration,” which occurs in the aforementioned infiltration station; on the other hand, it refers to the “embedding” or “block embedding” that occurs in the embedding station.
For embedding, the samples are placed into molds and the mold is filled with the embedding agent. The histological sample is then cooled so that the embedding agent can harden. To cool the histological samples they are, for example, placed onto a cooling plate of the embedding station. The result is to create an embedded block in which the sample is immobilized in stationary fashion. After hardening of the embedding agent, the sample can be sectioned with the microtome into individual thin sample sections, which in a subsequent step can be stained and investigated with a microscope.
To ensure that the sectioning operation with the microtome can be carried out precisely, it is necessary for the embedded block to remain in a hard state. In practice, a laboratory worker transports the cassettes individually from the embedding station to the microtome. Alternatively, it is known that the laboratory worker does not transport the cassettes individually, but instead places them from the cooling plate of the embedding station into a transport basket located next to the processing station. The transport basket is then transported to a microtome, with which the samples present in the transport basket can be processed.
With processing stations known from the existing art, the risk exists that, especially in warm regions, the embedded block may soften before the sample is processed using the microtome. Softening of the embedded block can occur when the samples are taken off the cooling plate and, for example, placed into the transport basket, and the latter is transported to the microtome only after a certain time has elapsed. A result of softening of the embedded block is that the sectioning operation with the microtome is difficult or in fact impossible.
A further disadvantage is the fact that transporting the cassettes individually between the embedding statin and the microtome is cumbersome and time-consuming. The use of transport baskets in turn has the disadvantage that additional components are used, which require additional storage space.